This invention relates to a telephone system in a vehicle, and more particularly, relates to a telephone system including a detachable handset.
Recently, the demand for providing a telephone system in a vehicle increased with the development of radio communication networks. However, telephone equipment as used in a home was being used for the telephone system in a vehicle. However, such conventional telephone equipment was not considered suitable for the uniqueness of a vehicle.
The telephone system in the vehicle becomes inconvenient for a vehicle driver if the driver cannot use the telephone system while the driver is driving the vehicle. Furthermore, the telephone system in the vehicle becomes inconvenient for vehicle passengers except for the driver, if the passengers cannot use the telephone system in the same manner in which they use the telephone system in their home.
Accordingly, it is preferable for the vehicle driver to execute "on-hook talking" which enables the driver to grasp a steering wheel with both hands. Further, it is preferable for the vehicle passengers, except for the driver, to execute "off-hook talking" that enables them to use the telephone system in the vehicle in the same manner as the telephone system in the home. A talker's voice should be picked up clearly over noises in the vehicle compartment in order to carry out "on-hook talking".
A telephone system capable of both "on-hook talking" and "off-hook talking" is disclosed in Japanese laid-open patent publication No. 82540/1986 published on Apr. 26, 1986. This telephone system includes two microphones and two speakers. The microphone for "on-hook talking" has a keen directivity in order to pick up the talker's voice clearly.
However, the use of two microphones increases the cost of a telephone system because the number of the parts is increased. Furthermore, the use of two microphones makes the electronic circuit complicated because an electronic circuit is required to select and process voice signals from the two microphones. Thus, two microphones are not preferable for a telephone system in a vehicle.
A telephone system capable of "on-hook talking" is disclosed in Japanese laid-open patent publication No. 141838/1980 published on Nov. 6, 1980. This telephone system positions a microphone close to the driver's mouth in order to pick up the driver's voice clearly during "on-hook talking".
However, if the microphone is positioned near the vehicle driver who wants to talk, the driver feels an unpleasantness from the closeness of the microphone. Especially, when the driver wants to talk, the driver may not be able to concentrate on driving because the microphone may disturb the driver's sight.